This application is based on and claims priority from Japanese Patent Application No. Hei-8-276718 filed on Oct. 18, 1996, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a data communication system that has a first information processing unit such as a computer and the like, and a second information processing unit such as a facsimile device with a printing function and the like. The present invention also relates to a data communication control method for such a data communication system. In particular, the present invention relates to the data communication system and the data communication control method wherein the second information processing unit transmits facsimile data and the like in response to transmission requests from the first information processing unit.
2. Description of Related Art
Multifunction peripheral devices, which have a plurality of functions and which act as peripheral equipment for computers, are now being developed. An example of such a multifunction peripheral device is a facsimile device that has a printing function. The facsimile device that has the printing function is configured to print data received from external devices such as a computer, a word processor and the like using its printer unit that usually prints facsimile data.
After receiving the facsimile data received from other facsimile devices and the like via a communication line, the facsimile device with the printing function prints facsimile data. In addition, the facsimile device with the printing function receives data transmitted by the computer and prints such data received from the computer.
Another type of multifunction peripheral device is the multifunction peripheral device that has expanded the functions of the facsimile device with the printing function. This type of multifunction peripheral device can send data received from a facsimile device or data read through a scanner to a computer and send facsimiles based on data transmitted by the computer. In this way, the computer can centrally control facsimile data receipt and transmission operations. The multifunction peripheral device is very useful in that it can transmit data read by a scanner to the computer, which can then edit the data, and subsequently receive edited data from the computer for facsimile transmission. In this way, with the multifunction peripheral device, facsimile data can be checked without the need for printing by displaying the data on the display of the computer and previously received facsimile data can be stored for subsequent usage.
The computer has main control over its communication operations with the multifunction peripheral device, which may be the facsimile device with the printing function. The computer transmits transmission requests to the multifunction peripheral device at predetermined time intervals. The computer subsequently receives data transmitted by the facsimile device in response to the transmission requests.
In addition, the computer checks for the existence of data to be transmitted to the multifunction peripheral device at predetermined intervals. When there is data that needs to be transmitted, the computer transmits the data to the multifunction peripheral device.
Meanwhile, for conventional data communication systems, the time interval at which the computer transmits the transmission requests is fixed regardless of the existence of data transmitted from the multifunction peripheral device. This does not pose a problem when the data to be transmitted from the multifunction peripheral device is, for example, status information data of the multifunction peripheral device which is small in size and whose content does not change very often. On the other hand, when a large amount of data such as facsimile data has been received by the multifunction peripheral device and needs to be transmitted to the computer, it takes a long time until the computer receives all the data and thus, high-speed operations cannot be performed.
The above problem is also holds true when transmitting data from the computer. That is, the interval for verifying the presence of data to be transmitted to the multifunction peripheral device is fixed regardless of the existence of the data to be transmitted. Therefore, the above setup hampers the high-speed transmission of data to the multifunction peripheral device.
Meanwhile, in parallel with performing data transmission and reception operations with the multifunction peripheral device, the computer also executes other operations and thus, transmission requests are transmitted at comparatively long intervals when there is no data to be received from the multifunction peripheral device. In the same way, when there is no data to be transmitted, the verification of the presence of data to be transmitted is preferably performed at comparatively long intervals.
In view of the foregoing problems in the prior art, it is a primary object of the present invention to provide a data communication system and a data communication control method for executing high-speed data reception operations. It is another object of the present invention to provide the data communication system and the data communication method for executing high-speed data transmission operations.
To achieve the aforementioned objects, one aspect of the present invention provides a data communication system that has a first information processing unit and a second information processing unit. The first information processing unit provides a transmission request to the second information processing unit. The second information processing unit receives the transmission request from the first information processing unit and sends response data to the first information processing unit in response to the transmission request. The first information processing unit provides a subsequent transmission request to the second information processing unit at a first time interval unless the second information processing unit sends the response data, and provides the subsequent transmission request to the second information processing unit at a second time interval shorter than the first time interval when the second information processing unit sends the response data.
In this way, the time needed for receiving data from the second information processing unit can be shortened when data is previously received. In this way, data reception operations can be performed at high-speed.
Preferably, the first information processing unit is further for determining if there is transmission data for the second information processing unit. The first information processing unit determines if there is transmission data at a third time interval when there is no transmission data during a previous determination operation and determines if there is transmission data at a fourth time interval shorter than the third time interval when there is transmission data during a previous determination operation.
In this way, the data transmission operations within the data communication system can be performed at high-speed.
Another aspect of the present invention provides a data communication method for facilitating communication between the first information processing unit and the second information processing unit. This method involves sending a transmission request from the first information processing unit to the second information processing unit, determining if the second information processing unit sends response data in response to the transmission request from the first information processing unit, sending a subsequent transmission request from the first information processing unit to the second information processing unit at a first time interval unless the second information processing unit sends the response data, and sending the subsequent transmission request from the first information processing unit to the second information processing unit at a second time interval shorter than the first time interval when the second information processing unit sends the response data.